whmcs integration plugin not working

Have just purchased the wp-whmcs integration plugin and its not working.

my website is http://www.mywebsite.com.au
whmcs is installed and working at http://www.mywebsite.com.au/clientarea.

I have also tried this plugin by setting up a sub-domain: http://www.clientarea.mywebsite.com.au (directs to whmcs folder) with no success. If I type in the sub domain, I get re-directed to my 404 error page and when I use the http://www.mywebsite.com.au/clientarea url, it removes the end of the url and I get this error:

Sorry this doesn’t look like a WHMCS site at [http://mywebsite.com.au/] Make sure your WHMCS Integration settings are pointing to the correct URL and that the WHMCS site is set for the Portal template in Setup | General.

PLEASE HELP!

PS - I have set the portal template... its definitely not that.